Heretofore, there has been in use metal ventilation apparatus which may be secured to roofs for various ventilation purposes. It is well known that if a building is warm inside and cold outside, and there is sufficient humidity within the building, this humidity will condense on contact with the cold surface of the building. This is usually most noticeable at the roof. All this condensed humidity or moisture will eventually cause the wood and other roof material to rot, thus necessitating steps to be taken to prevent such condensation from occurring. This is achieved by ventilating adequately all parts of the building all parts of the building where condensation is likely to occur.
In the roof, even when a vapor barrier has been used, condensation may still occur, so that all parts of the roof behind the insulation should be thoroughly ventilated. This can be achieved in part by providing for an air flow between the rafters, and under the sheathing and behind the insulation.
One of the more important needs for ventilation of a roof, to prevent condensation buildup in the space between the inside of a roof and the top of a layer of insulation, is based on the need to conserve enery used for heating and cooling of enclosed spaces. Water from condensation may cause certain types of insulation to decompose and lose efficiency, or, when the insulation is inert to water, water impregnation will cause insulation to conduct heat energy easily.
Apart from the condensation problem mentioned hereinabove, there exists of course the basic ventilation problem of supplying fresh air to indoor places and at the same time removing stale air from these places. For people to feel comfortable, they need fresh air which is free from dust, soot and odors. In addition, the air must not be too warm or too cool, and it must have the right amount of moisture.
The more people there are in a room, or the harder they work, the faster the air becomes stale. Stale air must be removed and replaced with fresh air. If the air outside is fresh, simply opening a window and perhaps turning a fan will ventilate the room. This of course is not possible if the room is on the inside of a building, or if the space or room to be ventilated is an attic or a crawl space.
The amount of air required for proper ventilation varies, depending on the room and the number of people in it. Under ordinary conditions, from 10 to 30 cubic feet (0.3 to 0.8 cubic meters) of fresh air must be supplied each minute for each person in the room.
The ventilation apparatus of the known type mentioned hereinabove is also helpful in removing harmful materials from the air. In addition to its use in connection with commercial buildings, it may also find use in mines or tunnels, and factories. In places such as mines or tunnels, poisonous gases may be present which must be removed before men can safely work there. In addition, factories may use such ventilation apparatuses to remove harmful fumes resulting from industrial processes.
One of the disadvantages of the prior art vent apparatus, is that it requires a minimum of two to four separate and distinct members or pieces which are relatively expensive to manufacture and which necessitate a relatively complicated process to construct together to form the desired vent apparatus. Moreover, such conventional vent apparatus is not sturdy, has limited duration of use, is susceptible of deterioration when exposed to the elements, and requires somewhat complicated interconnection procedures.
One prior art device known to applicants is disclosed in U.S. Pat. No. 3,593,478, issued in 1971 to Mason, for a three piece roof ventilator. Other prior art devices known to applicant are shown in U.S. Pat. Nos. 3,079,853, 3,311,047, and 4,000,688, which relate to ventilators adapted to extend along the ridge of a peaked roof constructed in an unconventional manner with a gap between roof boards at the peak of the roof, and U.S. Pat. No. 3,238,862 which discloses a six piece roof ventilator, having a molded plastic rectangular base sheet with a central flange, a molded plastic cover, a louvered metal sheet, and three rivets to hold the cover to the base sheet and entrap the metal sheet.
The problems, disadvantages and complexity alluded hereinabove are either eliminated or greatly alleviated by the present invention.